Conventional writing instruments, such as ball-point pens, have several limitations that limit their utility. When capped for storage and/or transport, they are 5″-6″ long—too long to fit into a shirt pocket without protruding, and too long to be comfortably stowed in a pants pocket. Since the longer writing barrel, as compared to the shorter cap, dominates the appearance of the instrument, the ability to use interchangeable components to change the appearance and/or functions of a conventional writing instrument is very limited. Because the potentially fungible cap is structurally and dimensionally subordinate to the non-fungible writing barrel, the opportunity to employ a variety of interchangeable caps with different visual, attachment and/or other functional features is foreclosed.
Moreover, the conventional writing instrument configuration, with its dominant writing barrel, often requires that the entire instrument be discarded when its ink supply is depleted. In a cap-dominant configuration, on the other hand, the shortened writing barrel itself becomes a secondary, disposable component, which is readily and inexpensively replaceable.
Finally, the dual coupling means, required for switching the elongated cap from frontal to rear connection on the writing barrel, enables various additional functional components to be attached to the back end of the writing instrument in its compact capped configuration, thereby expanding the versatile utility of the instrument.